Transcript of "Weather"

1.
WEATHER
INTRODUCTION
This PowerPoint is designed to review different
types of fronts and severe weather. Please view
the PowerPoint in its entirety, as well as,
completing the activity and quizzes, and viewing
the simulation.
You may go back and review the PowerPoint at any
time.
This is intended to help you with your Chapter 24
test.

3.
WEATHER
According to Dictionary.com, weather is defined as “The state of
the atmosphere at a given time and place, with respect to
variables such as temperature, moisture, wind velocity, and
barometric pressure.”

4.
FRONTS
 Density differences keep two air masses separate
when they meet.
 One air mass must collide with another air mass.
 The kind of front that forms is determined by
how the air masses move in relationship to each
other.

5.
TYPES OF FRONTS
 Cold Front - The front edge of a moving mass of
cold air that pushes beneath a warmer air mass
like a wedge.
 Warm Front – The front edge of advancing warm
air mass that replaces colder air with warmer air.
 Stationary Front – A front of air masses that
moves either very slowly or not at all.
 Occluded Front – A front that forms when a cold
air mass overtakes a warm air mass and lifts the
warm air mass off the ground and over another
air mass.

7.
FAST MOVING COLD
FRONT
 Clouds will form if the warm air is moist
 Large cumulus and cumulonimbus clouds
 Storms are usually short-lived and sometimes
violent
 Air behind cold front is noticeably colder and
drier

8.
WARM FRONT
 Less dense warm air rises over the cooler air
 Clouds may extend far ahead of the base of the front
 Stratus clouds
 Produces gentle precipitation over a large area
 May cause violent weather
 Air behind the warm front is warmer and more moist

10.
STATIONARY & OCCLUDED
FRONTS
Stationary Front
 Weather is similar to a
warm front
 Produces precipitation
over a large area
 May cause violent
weather
Occluded Front
 Wide variety of weather
 Thunderstorms possible
 Usually their passage is
associated with a drying
of the air mass

13.
PRACTICE PREDICTING
THE WEATHER
Predict the Weather
Directions:
1.) Click on the picture above
2.) Once the webpage is open, click on “Predict the Weather”
3.) Click on “Start Level 1”
4.) Once you are finished with level one, bring me your
computer so I can record your quiz score
5.) Repeat for Levels 2 & 3

14.
QUIZ: FRONTS
CLICK ON THE CORRECT ANSWER
1.) What is most likely to occur when a mass of cold air
moves into a region occupied by warmer air?
A warm front will form, and there will be intense
precipitation.
The air masses will mix rapidly, forming an air mass of
intermediate temperature.
The boundary between the two air masses will be a zone
of intense high pressure.
A cold front will form, as warm air is forced upward.
All of the above.

17.
QUIZ: FRONTS
CLICK ON THE CORRECT ANSWER
2.) A front that is characterized by stratus clouds, and
gentle precipitation for a long time is a(n)
_______________ front.
cold
stationary
warm
occluded
none of the above

20.
QUIZ: FRONTS
CLICK ON THE CORRECT ANSWER
3.) Storms along a cold front are usually short-lived and
sometimes violent, while storms along a warm
front
are short-lived and weak.
produce precipitation over a large area, and are
sometimes violent.
are narrow, producing little rain and are always violent.
are long-lived, but always weak.

23.
QUIZ: FRONTS
CLICK ON THE CORRECT ANSWER
4.) A front that forms when a cold air mass overtakes
a warm air mass and lifts the warm air mass off
the ground and over another air mass is called
a(n)
warm front.
stationary front.
occluded front.
cold front.

27.
THUNDERSTORMS
 Thunderstorm – a heavy storm that is accompanied by rain, thunder,
lightning, and strong winds.
 Thunderstorms develop in 3 stages
 Cumulus Stage – warm, moist air rises, and the water vapor within the air
condenses to form a cumulus cloud
 Mature Stage – condensation continues as the cloud rises and becomes a
dark cumulonimbus cloud
 Heavy, torrential rain and hailstones may fall
 Strong updrafts continue to rise, downdrafts form as air is dragged
downward by the falling precipitation
 Dissipating Stage – strong downdrafts stop air currents from rising
 Thunderstorm dissipates as the supply of water vapor decreases

29.
LIGHTNING
 When clouds discharge electricity
 Clouds must have areas that carry distinct electrical
charges
 Upper part of the cloud usually carries a positive
charge
 Lower part of the cloud mainly carries a negative
charge
 A huge spark travels within the cloud or between the
cloud and ground to equalize electrical charges

31.
TORNADOES
 Tornado – a destructive rotating column of air that has
very high wind speeds and that is visible as a funnel-
shaped cloud
 This is the most violent, and shortest-lived severe storm
 Forms when a thunderstorm meets high-altitude
horizontal winds
 Horizontal winds cause the rising air to rotate
 A storm cloud may develop a narrow, funnel-shaped,
rapidly spinning extension that reaches downward

32.
TORNADOES CONT.
 Tunnel will move in a wandering, haphazard path if it
touches the ground
 Generally covers paths not more than 100 m wide
 Usually, everything in that path is destroyed
 Destructive power of a tornado is mainly due to the
speed of the winds in the funnel
 Winds may reach speeds of more than 400 km/h
 Most injuries and deaths caused by tornadoes occur
when people are trapped in collapsing buildings or are
struck by objects blown by the wind

34.
HURRICANES
 Hurricane – a severe storm that develops over tropical
oceans and whose strong winds of more then 120 km/h
spiral in toward the intensely low-pressure storm center
 Warm, moist air over the ocean rises rapidly
 Fully developed hurricanes consist of a series of thick
cumulonimbus cloud bands that spiral upward around the
center of the storm
 Winds increase toward the center, or eye, of the storm
and reach speeds of up to 275 km/h along the eyewall
 The eye itself is a region of calm, clear, sinking air